A method of cementing a wellbore penetrating a subterranean formation, the method comprising: injecting into the wellbore an oil-based fluid; injecting into the wellbore a cement spacer fluid comprising an aqueous carrier, an oil swellable elastomer, and a viscosifier; contacting the oil-based fluid with the cement spacer fluid to swell the oil swellable elastomer in the cement spacer fluid; injecting a cement slurry into the wellbore; and allowing the cement slurry to set.